The present invention relates to a mixing of a plurality of musical signals from a variety of record players and CD players in real time, or providing an audio mixer which may be utilized in a disc jockey rendition as found in a dancing club, radio broadcasting programs or the like, for example, to change a musical signal being performed into another momentarily to aid some performance, in particular, an audio mixer of excellent maneuverability.
FIG. 1 shows an exemplary functional arrangement of a conventional audio mixer. An audio mixer 10 shown includes audio input terminals 11 and 12 for two channels, to which audio signals CH1, CH2 are input and then subject to effect algorithm processors 21, 22 which add appropriate acoustical effects thereto before they are added together at a suitable addition ratio in an addition processor 23. An effect algorithm processor 24 adds an appropriate acoustical effect to the added signal, which is then delivered as an audio signal from an output terminal 17.
Effect algorithm processors 21, 22, 24 and the addition processor 23 are implemented with a digital arithmetic unit 20, which is commonly referred to as DSP (digital signal processor). Audio signals which are input to the input terminals 11 and 12 (which are generally both stereo signals and their signal paths comprise stereo signal transmission paths) are fed through volume controls 13, 14, respectively, to A/D converters 15, 16, respectively, where they are converted into digital signals to be input to the digital arithmetic unit 20. The effect algorithm processors 21, 22 apply the addition of reverberations, echoes, chorus effects, distortions or the like, for example, to both or either one of the audio signals. Output signals from the processors 21, 22 are added together at a suitable addition ratio in the addition processor 23, and the effect algorithm processor 24 again applies an appropriate acoustical effect (such as volume and tone control, for example) to the added signal to be fed to a D/A converter 18 where the latter is converted into an analog signal, which is then delivered as an analog audio signal from the output terminal 17.
An operational mode of the digital arithmetic unit 20 is set up by a controller 26 which principally comprises a microcomputer. As is well known, the controller 26 comprises a central processing unit 26A, a rewriteable RAM 26B, a read only memory ROM 26C, an input port 26D and an output port 26E.
An entry setting unit which is mounted on a control panel 30 is connected to the input port 26D. To exemplify the entry setting unit, it may includes as a required minimal arrangement, a mode changeover switch 31 and three sliding variable resistors 32, 33, 34. By operating the mode changeover switch 31 to a selected position, the operational mode of the digital arithmetic unit 20 can be changed. Thus, when the mode changeover switch is thrown to a selected position, each of the effect algorithm processors 21, 22, 24 can be independently configured to operate as a variable low pass filter, a variable high pass filter or as a variety of effecters such as an effecter adding reverberations, an echo adding effecter or a sound distorting effector.
The selected operational mode is indicated on a indicator 27 which is connected to the output port 26E, whereby a user can know which mode is established by recognizing the mode indication on the indicator 27. An entry setting unit which sets up a variety of parameters in addition to the mode changeover switch 31 and the sliding variable resisters 32 to 34 in order to achieve various other effecter operations is also known, but will not be described herein for the sake of simplicity.
A program which causes the microcomputer defining the controller 26 to operate in accordance with a selected mode is stored principally in ROM 26C.
For example, when the mode changeover switch 31 is thrown to the position No. 1, the operation in a cross fade mode is established. In a cross fade mode, the addition ratio between the signals CH1 and CH2 which are input to input terminals 11 and 12 can be changed in a differential manner. A functional arrangement of the digital arithmetic unit 20 when it is set up in the cross fade mode is shown in a simplified form in FIG. 2. When this mode is set up, the effect algorithm processors 21, 22 and 24 are set up to freely pass the input signals therethrough, and the addition processor 23 is replaced by a condition which is equivalent to a variable resistor having opposite ends to which the signal CH1 and CH2 are input, respectively, and having a movable tap from which a synthesized signal is delivered. Thus, when the cross fade mode is established, an execution of the program by the microcomputer causes the digital arithmetic unit 20 to perform the addition in accordance with the sliding position of the movable tap on the sliding movable resister 32.
Accordingly, in the cross fade mode of the addition processor 23, the volumes of the signal CH1 and CH2 can be controlled in a differential manner through the controller 26, by operating the sliding movable resister 32. In other words, a switching from the signal CH1 to the signal CH2 or from the signal CH2 to the signal CH1 can take place in a gradual manner. Such switching is referred to as cross fade.
FIG. 3 shows a functional arrangement of an operational mode in which the function of changing the frequency response of the filters in the respective input channels is added to the cross fade from the signal CH1 to the signal CH2. This operational mode may be considered as being established when the mode changeover switch 31 shown in FIG. 1 is thrown to the position No. 2, for example. In this instance, the digital arithmetic unit 20 is configured so that the functions of a variable low pass filter and a variable high pass filter are imparted to the effect algorithm processors 21 and 22, respectively. In the example shown in FIG. 3, the variable low pass filter function is imparted to the effect algorism processor 21 which is associated with the signal CH1 while the variable high pass filter function is imparted to the effect algorithm processor 22.
The cut-off frequency of the variable low pass filter which is formed by the effect algorithm processor 21 can be moved to a higher or a lower frequency by sliding the variable resistors 33 mounted on the control panel 30. Similarly, the cut-off frequency of the variable high pass filter which is formed by the effect algorithm processor 22 can be moved to a higher or lower frequency by sliding the variable resisters 34. Accordingly, when the sliding variable resistors 32 which controls the addition processor 23 is operated to switch gradually from the signal CH1 to the signal CH2 while simultaneously operating the sliding variable resistors 33 and 34 in a differential manner (or moving the slider positions differentially) to lower the cut-off frequencies of both the variable low pass filter and the variable high pass filter, the tone in the signal CH1 which contains a middle and a high pitch region component change into ones in which the lower pitch components are principal while the signal CH2 which originally contains only high pitch region components gradually changes into ones which include both middle and low pitch region components, thus producing tones which are clearly perceivable.
Accordingly, when the sliding variable resistors 33 and 34 are operated in a differential manner while operating the sliding variable resistor 32, a switching of the signal tones will be felt more naturally than when the cross fade takes place simply in terms of the volumes, thus realizing a cross fade with a more excellent rendition in audible sensation.
FIG. 4 shows a functional arrangement of another operational mode which is established by throwing the mode changeover switch 31 shown in FIG. 1 to the position No. 3 to add the function of adding reverberations only to those signals which fade out during the cross fade. At this end, the effect algorithm processor 21 (or 22) is set up as a reverberation or echo effecter. Specifically, FIG. 4 shows that the effect algorithm processor 21 includes a reverberation adding unit 21-1, and an addition processor 21-2 which achieves a cross fade between a reverberation added tone and direct tone which is not added with a reverberation.
The addition processor 21-2 which is configured in the effect algorithm processor 21 can be controlled by sliding the sliding variable resistor 33 mounted on the control panel 30 to change the addition ratio or mix balance between the reverberated tone and non-reverberated or direct tone. For example, when the cross fader is moved in a direction from the signal CH1 toward the signal CH2, the cross fader may be operated, and simultaneously, the sliding variable resistor 33 may be moved from a condition in which the proportion of the reverberated tone and the direct tone is equal to 0% and 100%, respectively, to a condition in which the proportion is reversed, or, the reverberated tone occupies 100% while the direct tone occupies 0%. In this instance, the tones in the signal CH1 gradually decrease in volume while shifting to reverberated tones, but the tones in the signal CH2 simply increases in the volume.
It will be seen that these operations not only result in a simple transition of the volume from the signal CH1 to the signal CH2 during the cross fade, but there is obtained a transition in which the signal CH1 changes into reverberated tones which are gradually deepened and are further moving away, and are replaced by the tones of the signal CH2. This realizes a more natural and effective cross fade.
FIG. 5 shows a functional arrangement of an effect insert mode established for the digital arithmetic unit 20 when the mode changeover switch 31 shown in FIG. 1 is thrown to the position No. 4. In the example shown in FIG. 5, the effect algorism processor 22 associated with the signal CH2 is arranged to be a pass-through condition while effect changeover switches SW1 and SW2 are connected before and after the effect algorithm processor 21 in the path of the signal CH1. In this manner, by changing the switches SW1 and SW2, a switching between a condition in which the effect algorithm processor 21 is connected and another condition in which it is replaced by a pass-through condition is achieved. The effect changeover switches SW1 and SW2 are changed by operating a switch 35 which is included in the control panel 30.
The effect function of the effect algorithm processor 21 may be a mode of the addition of the reverberated tones, for example. By operating the sliding variable resistors 33 and 34, the degree of reverberations, namely, how deeply or weakly the reverberations are applied and the time over which the reverberations are attenuated can be controlled.
When it is desired to add reverberations to the signal CH1, the switch 35 may be depressed, for example, and a resulting contact on signal may be applied to the controller 26 to change the effect changeover switches SW1 and SW2 so that the signal CH1 is passed through the effect algorithm processor 21 before it is applied to the addition processor 23. When the sliding variable resistors 33 and 34 are operated simultaneously, reverberated tones are added to the signal CH1 depending on the sliding position, thus changing the depth of reverberations and the attenuation interval. In this instance, the addition ratio by the addition processor 23 is controlled by the sliding movable resistor 32.
It will be seen that a conventional audio mixer suffers from a poor maneuverability in that its operation is troublesome because the maneuver principally comprises operating the sliding movable resistors 32,33,34 and the switch 35 to implement the cross fade, to change the cut-off frequency of the filter or to change the depth to which the reverberations are added.
The maneuver is troublesome in particular in the arrangement of FIG. 3 where the cut-off frequencies of both variable low pass filter 21 and variable high pass filter 22 must be changed in a differential manner while simultaneously carrying out the cross fade, thus requiring that the three sliding variable resistors 32, 33, 34 be operated at the same time.
In the arrangement of FIG. 2 where a simple cross fade operation takes place, what occurs is a gradual reduction, for example, of the tones in the signal CH1 to be replaced by a gradually increase in the tones of the signal CH2, resulting in a monotonous changeover of tones, which is unnatural disadvantageously. In particular, when the tones in the both signals CH1 and CH2 are mixed together, a simple addition of two input musical tones result in an intricate sound.
In carrying out the cross fade, when the maneuver is made to change the cut-off frequencies of both the variable low pass filter 21 and the variable high pass filter 22 in the same direction as indicated in FIG. 3, if the cross fade is implemented in synchronism, a smooth switching of tones results to improve the audible sensation, which is advantageous. What is brought forth in the actual audible cross fade shown in FIG. 3 will be described below.
When musical tunes as from CD or records are input to the input terminal 11 and 12, it will be noted that signals from the musical instruments which are used in these musical tunes include inherent frequency bands. For example, a bass drum, a cymbal and a guitar or a vocal has its principal signal component in the low pitch tone region, the high pitch tone region, and the middle pitch tone region, respectively. Rather than reducing the volume of the signal CH1 and shifting to the signal CH2 in a simple manner, in the cross fade shown in FIG. 3 in which the cut-off frequencies of the filters in the respective channels are varied, there is an effect that the tones fade out from the signal CH1 in a sequential manner beginning with the high pitch region signal components in the musical instruments while tones from the signal CH2 appear in a opposite sequence beginning with the high pitch signal components of the musical instruments. However, to realize this to effect, the three sliding variable resistors 32, 33, 34 must be operated simultaneously, thus involving the drawback of a difficult maneuver.
In the arrangement shown in FIG. 4, the cross fade while leaving the reverberations allows the tones in the signal CH1 to be gradually changed into reverberated tones rather than simply decreasing the volume thereof, thus achieving an effective cross fade in audible rendition in that the signal CH1 moves farther away while the tones in the signal CH2 come into appearance. However, again the two sliding moveable resistors 32, 33 must be operated simultaneously.
In the effect function adding mode shown in FIG. 5, the switch 35 must be depressed while simultaneously operating the sliding variable again, the maneuver is troublesome and the operator will experience a substantial fatigue when he works over a prolonged length of time.
It is an object of an invention to eliminate inconveniences of the prior art as mentioned above, by providing an audio mixer which can be maneuvered in a simple manner.